The present invention relates to a method for adjusting the drill feed support of a rock drilling unit to a position a given distance from a rock surface in which holes are to be drilled to a depth which is read by means of a measuring instrument. Further, the invention relates to a means for performing such method.
When drilling holes in rocks the feed support with a drill stem and drill stem guides is moved sideways from hole to hole. This sideways movement should take place at such a distance from the rock surface that the drill and feed support with stem guides do not collide with the rock and become damaged. When the drill has reached a correct position for drilling another hole, it is important that the feed support with its front end stem guide is moved as close to the rock surface as possible, without contacting the rock surface.
This distance by which the feed support has to be moved forward for setting of the drill in a start drilling position, will be different from one hole to another dependent on the exterior of the rock surface. When using automatically operated drilling units there is a need for this forward movement to be controlled automatically, particularly when the drilling unit has more than one drill boom with feed support.
Such automatic forward movement of the feed support has not been known previously, but may be obtained in theory by means of a sensor which either measures the distance from the feed support to the rock surface, or detects if this distance is less than a predetermined or defined length. An example of a practicable distance measuring instrument that includes a sensor, is a buffer which may be mounted on the front end of the feed support, and which may be resilient to give a signal when contacting the rock. Another example is a distance measuring sensor mounted in the front end stem guide. A further example is an arrangement including mechanical feelers which give a signal when reaching the rock.
A common feature of these solutions is that they require additional elements on the feed support. Such elements make the drill equipment more complicated. These elements in addition will make the equipment more expensive, as they are situated on an extremely exposed location where they easily get damaged when colliding with the rock or when being hit by falling stones, or they become disabled by being covered with drilling mud, and thus have to be replaced often.